Just to prove how relatively trivial it would be for you guys, I wrote a Google Checkout gateway for Nexus yesterday afternoon using the official Google APIs / libraries and it works great, i'm now running it on my site.

This is a fully automated gateway, processing the callback XML payloads from Google etc...

Having started coding this myself I know this isn't a huge amount of work... Google Checkout has a very fully featured set of APIs. I had this working on a previous IP.Nexus in fact, but haven't updated it for 2.3.1 because a) your documentation on payment gateways is so awful and b) I'd love to see you guys do it!

I would even be willing to pay a small additional charge for the gateway, so... pretty please? :)